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    <title>ShellCheck: SC2205 – `(..)` is a subshell. Did you mean `[ .. ]`, a test expression?</title>
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    <h1>SC2205 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC2205">See this page on GitHub</a>
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    <h2
id="-is-a-subshell-did-you-mean----a-test-expression"><code>(..)</code>
is a subshell. Did you mean <code>[ .. ]</code>, a test expression?</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2205.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="cf">if</span> <span class="kw">(</span> <span class="ex">1</span> <span class="at">-lt</span> 2 <span class="kw">)</span></span>
<span id="cb1-2"><a href="SC2205.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="cf">then</span></span>
<span id="cb1-3"><a href="SC2205.html#cb1-3" aria-hidden="true" tabindex="-1"></a>  <span class="bu">echo</span> <span class="st">&quot;1 is less than 2&quot;</span></span>
<span id="cb1-4"><a href="SC2205.html#cb1-4" aria-hidden="true" tabindex="-1"></a><span class="cf">fi</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2205.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="cf">if</span> <span class="bu">[</span> 1 <span class="ot">-lt</span> 2 <span class="bu">]</span></span>
<span id="cb2-2"><a href="SC2205.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="cf">then</span></span>
<span id="cb2-3"><a href="SC2205.html#cb2-3" aria-hidden="true" tabindex="-1"></a>  <span class="bu">echo</span> <span class="st">&quot;1 is less than 2&quot;</span></span>
<span id="cb2-4"><a href="SC2205.html#cb2-4" aria-hidden="true" tabindex="-1"></a><span class="cf">fi</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>Tests like <code>-eq</code> to check numeric equality or
<code>\&lt;</code> for string comparison only work are actually
parameters to the <code>test</code> command, and only work as tests in
that context. <code>[</code> is an alias for <code>test</code>, so
you'll frequently see them written as <code>[ 1 -eq 2 ]</code>.</p>
<p><code>( .. )</code> is completely unrelated, and is a subshell mostly
used to scope shell modifications. They should not be used in
<code>if</code> or <code>while</code> statements in shell scripts.</p>
<p>If you wanted to test a condition, rewrite the <code>( .. )</code> to
<code>[ .. ]</code>.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>This error is triggered by having a binary operator as the first
parameter in a subshell, and could falsely trigger on e.g.
<code>if ( grep -eq "foo|bar" file )</code>. In these cases, check
whether the subshell is actually needed.</p>
<p>Note that there's a similar looking error <a href="SC2204.html">SC2204</a>
with a low false positive rate.</p>
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    <p style='font-size: 80%'><a href="../index.html">ShellCheck</a> is a static analysis tool for shell scripts. This page is part of its documentation.</p>
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